Field of the Invention
The present invention relates to a truss structure which can be stowed within a small space in the folded condition and can be deployed in one or two directions and, more particularly, to a deployable truss structure which can easily be deployed in outer space and can take various shapes in the deployed condition.
The truss structure according to the invention is designed as a medium-sized or large space building such as a space colony, a solar power generating satellite, a huge antenna or a space station. It may also be used as a transportable, makeshift building on the ground.
The components of a space building are boosted into outer space from the earth. Hence, they must meet the following requirements:
(1) As light as possible PA1 (2) Small enough to be stowed in a spacevehicle PA1 (3) Small in the folded condition PA1 (4) Easy to assemble into a building PA1 (5) Rigid in the deployed condition.
Truss structures are the most promising for a large space building. A so-called nestable column is one type of truss structure. To assemble nestable columns into a building in outer space is not easy. Robot may be used to assemble such a building. If robots are employed for this purpose, at least one astronaut must supervise them, endangering himself. Hence, a demand has been made for a truss structure which is automatically or semiautomatically deployable in outer space though it cannot be packaged very tightly. To meet this demand, various truss structures have been invented which can be deployed in one direction. One of them is "Astromast (tradename)" disclosed in Japanese Patent Publication Sho No. 49-26653 and in U.S. Pat. No. 3,486,279. Truss structures deployable in two directions are still in their embryonic stage.
Despite the great demand, there are no practial truss structures deployable in two directions. It is more greatly demanded that a two-dimensionally deployable structure be packaged small than it is desired that a truss structure depolyable in one direction be small. Further, the one-dimensionally deployable structures available at present cannot be stowed within a small space.
The one-dimensional truss structures are divided into two types. The first type comprises rigid members and joints connecting trusses. The second type comprises flexible, foldable members and no joints. Both types have their own drawbacks. The members of the first type have but insufficient buckling strength. The second type is not so rigid as desired.
In space, a parabola antenna deployed in space may have a shape different from the shape it takes when assembled on the ground, since no force of gravity acts on it in outer space. In addition, it may undergo a thermal deformation in outer space. Accordingly, it is desired that its shape can be adjusted in space.
A deployable truss structure has been proposed which comprises members arranged along the edges of an imaginary rectangular parallelepiped and diagonal members arranged in the faces of the parallelepiped. This is relatively rigid, but each diagonal member needs a mechanism which allows it to expand and contract. Due to the use of such mechanisms, it is inevitably complex and relatively heavy. For the same reason, it occupies a relatively large space when folded.